Car Doctor: Tire shops are torqueing lugs nuts more than the manufacturer recommends
Q: For the past several years, I have had run-ins with service people at the tire store. When I go in for tire balancing, I write 76 foot-pounds lug nut torque, which is what Toyota calls for.
When I get the car back, I use my old-style torque wrench, which has a needle point scale that goes from 0 to 140 pounds. When I try to loosen the lugs, they don’t break free to well past the 140-pounds mark on my torque wrench scale.
Last week the same thing happened when I purchased new tires. They had the lug nuts tightened to about 160 or 170 pounds.
I have two torque wrenches, one a needle point and the click wrench. When I test them together, they are right on. I do believe that the wheel studs are now damaged.
I have had this happen to me at two different tire shops. Is it common practice for tire shops to torque lug nuts to more than twice the manufacturer's stated torque rating? Is this practice common throughout the tire industry?
A: There may be two issues: one with the shop and one with the way you are checking wheel torque.
If the shop used an impact wrench, it is certainly possible that the lugs are over torqued. Most good shops will run the lugs up snug with an impact wrench and finish tightening the wheel with a torque wrench.
What you are trying to do is measure breakaway torque. The torque numbers will be higher because breakaway torque measures static torque (the fastener is not moving), while the tightening torque is a dynamic value (because the fastener is still moving).
The best method to check any fastener torque is to mark — in this case the nut and stud location — and loosen the lug and then retighten the lug to the previous mark to determine the actual tightening torque.
Q: I have a Lexus RX350. I use regular unleaded gasoline (usually Mobil).
My wife and I are driving to Virginia from our home in Rhode Island at the end of the month. My brother told us it would benefit the engine to run the gas down near empty, then fill the engine with high octane (Super Plus) gasoline and make the highway drive (about 350 miles) on that tank of gas. He claims it will benefit the engine and “clean out the gunk.” Is he correct?
A: Not to disagree with your brother but, no.
Mobil is one of the brands of gasoline that is considered TopTier. TopTier (toptiergas.com) gasoline has additional additives that will help keep the engine combustion chamber clean. Your Lexus RX 350 will run just fine on 87 octane fuel.
Q: I have a 2020 Acura RDX SH-AWD with a 2.0-liter engine. The vehicle has 13,000 miles on it. The Acura dealer is indicating that the rear differential fluid needs to be changed every 15,000 miles. I am told the cost of this is around $300. The “maintenance minder” confirms this.
I do not tow anything or drive in mountainous areas. If I did, the recommendation is every 7,500 miles. This seems questionable to me. What do you think?
A: It seems as if the Acura service department is combining two recommendations. I would follow that Acura Maintenance-Minder and wait for sub-menu 6 to come up.
Depending on how you drive, this could happen between 15,000 and 50,000 miles.
Here is what Acura states: Driving in mountainous areas at very low vehicle speeds or trailer towing results in a higher level of mechanical (shear) stress to fluid. This requires rear differential fluid changes more frequently than recommended by the Maintenance Minder.
If the vehicle is regularly driven under these conditions, have the rear differential fluid changed at 7,500 miles, then every 15,000 miles.
Regarding cost, the vehicle uses a little less than two quarts of fluid and will take about 30 minutes to service the differential. The fluid is pricey and labor rates are now hovering at $150 per hour and rising.
Q: Recently, you answered a question about starting a car that had been sitting for a length of time. Part of your response included draining the old gas. This good advice applies to small engines and marine engines, as well as automobiles. The problem that I have experienced is how to dispose of that bad gasoline once the tank is drained? Any suggestions?
A: Whenever in doubt, see if your city or town has a hazardous waste day to dispose of the bad/old gas.
With my seasonal equipment, I always start with fresh gas.
To dispose of that gasoline (if it was stored in a sealed container), I add about a gallon of the old gas at a time to my cars and let the engine dispose of it for me.
If you want to be extra careful, filter the gasoline through a coffee filter and add some isopropyl gas line antifreeze to remove any moisture.
If the old gas has lots of water in it or smells and looks like varnish, don’t risk running it in your car. Find a disposal site.
John Paul is the AAA Northeast Car Doctor. He has more than 40 years of experience in the automobile industry and is an ASE-Certified Master Technician. Write to John Paul, The Car Doctor, at 110 Royal Little Drive, Providence, RI 02904. Or email jpaul@aaanortheast.com and put “Car Doctor” in the subject field. Follow him on Twitter @johnfpaul or on Facebook.
This article originally appeared on The Providence Journal: Are tire shops are torqueing lug nuts more than torque rating?
